Aluminates as ester-interchange catalysts in making polyesters



ALUMINATES AS ESTER-INTERClIANGE CATA- LYSTS IN MAKING POLYESTERS Norman Fletcher, Blackley, Manchester, England, as#

signor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain N Drawing. Application April 16, 1954, Serial No. 423,330

' 1'0 mass is stirred and 0.045 part of sodium aluminate added,

after which the temperature is raised to 280 C. in two Claims priority, application Great Britain April 30 1953 5 Claims. (Cl. 260-75) This invention relates to an improved process forthe manufacture of highly polymeric polymethylene terephthalates, particularly polyethylene terephthalate. a

The highly polymeric polymethylene terephthalates are linear polyesters having great value as fibre and filmforming material. They are made by a polycondensation capable of undergoing a condensation reaction with itself e. g. bis(hydroxy alkyl) terephthalateJ The derivative of terephthalic acid may be formed byany known method e. g. by reacting a glycol with terephthalic acid or by an ester interchange reaction using a glycol and an ester of terephthalic acid, or by reacting an alkylene oxide with terephthalic acid.

Of the highly polymeric polyrnethylene terephthalates that derived from ethylene glycol and terephthalic acid be added'at thestart oftheester interchange reaction it v I ,Our' invention is illustrated but not limited by the followingexamples inwhich all parts are by weight:

I ioopans bf bis-ny'drexe h l tereplith'alate are melted a under oxygen free nitrogen in a 4 litre vessel fitted with a stirrer and having two outlets one of which is connected to a vacuumt'pumpand the other closedl. ,Themolten hours. When the temperature reaches 245 C. the vacuum pump is broughtinto action andthe pressure reduced Fro below 1-mm.,'the1reaction continuing for 1% hours; "The stirrer is then stopped; the vacuum pump. -disc'onnected reaction by heating a derivative of terephthalic we" 7 a temperature of150? C.,' 0.08 ,part of calcium acetate, 0.06 part of calcium aluminate are added, dispersed in a i. e. polyethylene terephthalate is the ,best known 'commercially as a fibre and film-forming material. Inthe manufacturing process most commonly used to make polyethylene terephthalate the first step is an ester interchange reaction between ethylene glycol -and dimethyl terephthalat'e to form -bis(beta-hydroxyethyl) terephthalate. This compound is then polycondensed under reduced pressure and at a high temperature.

To carry out the manufacture of these linear polyesters in a reasonable time, it is necessary to use a catalyst. Many catalysts have been disclosedfor this purpose but.

we have found that those giving a rapid production rate also tend to bring about a rapid rate of polymer degradation. Another disadvantage is that many of theknown catalysts produce a polymer having a yellowish colour or a cloudy appearance. In the manufacture of fibers a colour as near white as possible is required and for film making a clear bright polymer is necessary.

The present invention comprises an improved process for manufacturing highly polymeric polymethylene terephthalates by polymerising. a bis(hydroxy alkyl) terephthalate using as a catalyst an aluminate, which is soluble in the reaction mixture. 5

It is preferred that the aluminate should be readily soluble in glycol. The even distribution of the catalysts is aided by using them in finely powdered form, dispersed 350 litre scale ester interchange was completed in seven a hours'and thejpolymerisation.at 280 C. took six hours.

or dissolved in glycol. Suitable aluminates include those of the alkali metals and alkaline earthmetals.

addition'to the aluminate .an ester interchange; catalyst V Example 1.

quenched in water, dried and cut into chips.

The product is a clear polymer, softening point 265- ourican be melt-spun useful textile fibres.

and the gas space above the molten material filled with.

nitrogen under pressure-On opening the other outlet,

molten polymer is extruded by the nitrogen pressure} i C., intrinsicviscosity (determined in o-chlorphenol) l.

Filaments of good-colour can be meltspun from the polymer and drawn into useful; textile yarns;

ww Q parts of dim ethyl terephthalate and f75,-parts of ethylene glycol are melted under'deoxidised nitrogen.-' At one part of ethylene ,iglycoL, Ester interchange is carried out within a temperature range of 1 609-2159 0. at V atmospheric pressure. Methanol is distilled off,*the 'reace f tionbeing completed in 3 /2 hours. I V Thebis-hydroxyethyl terephthalate is transferred to a" stainless'steel 4 litre rvessel and 05 part of titanium dioxideadded, dispersed'in ethyleneglycol. Polymerisation. is carried out as inExample 1, the time taken being 7 2 hours.

(The product is a white polymer, intrinsic-viscosity 0.69

(determined in.o- 'chlo1phen0l). Filaments o f good 001- y from the polymer'and' drawn into a Example 3 calcium acetateand 003 part sodiumaluminate; On the Notitaniurn dioxide was added.

;A clear product is obtained of intrinsic viscosity 0.70

, scalev using as" catalyst 0.06% of zinc'aluminate in place of 0.045 part of sodium aluminatepand with the addi- 'tion o'f 0.5 part oftitanium dioxide. A fter the applica- "tion ofva'cuum (at 245C.) thetemperatureis raisedto To ensure that a near white polymeri s obtainedfthel:

275 C. Polymerisa tion is carried out for 1% hours at apressure below 1 The" product is textile yarns,

V Theintrinsic viscosity 'n, referred to in the examples,

should be used. Many such catalysts are known but we a 5 is determined insolution in'o-chlorphenol at 25 C. and

serves asa measure ofthe degree of polymerisation. It is calculated according to the formula 2,711,402 Patented June 21, V

'The proces's of Example 2 is repeated using 008 part i minaand the polymer is extruded as in a clear polymer, intrinsic viscosity 0.65 i (determined in -o-chlorphenol).. Filaments. of good colour can be melt-spun from the polymer and drawn into where n5=specific viscosity i. e.

flow time of solution flow time of o-ehlorphenol and c=concentrati0n of solution in gins. per 100 ml.

The polymers made according to the foregoing examples were compared with polymer made under the same conditions using the Well known catalyst, lead oxide. in all cases the polymer colour using an aluminate catalyst, was superior to that obtained using lead oxide.

What we claim is:

l. A process according to claim 3 wherein the final polyester contains less than 0.05% by weight of aluminium metal.

2. A process according to claim 3 wherein the highly polymeric polymethylene terephthalate is polyethylene terephthalate.

3. A process for the manufacture of highly polymeric polymethylene terephthalates which comprises polymerizing '21 bis (hydroxy alkyl) terephthalate in the presence of an aluminate which is soluble in the reaction mixture as a catalyst, said aluminate being selected from the group consisting of the alkali metal and alkaline earth metal aluminates and Zinc aluminate.

4. The process of claim 3 wherein said aluminate catalyst is sodium aluminate.

5. A process for manufacturing highly polymeric polyme'thlyene terephthalates which comprises the steps of forming a his (hydroxy alkyl) terephthalate from a glycol and an alkyl ester of terephthalic acid in the presence of calcium acetate as an ester interchange catalyst and thereafter polymerizing the bis (hydroxy alkyl) tel-eph- '2 thalate by heating under subatmospheric pressure in the presence of an aluminate which is soluble in the reaction mixture as a catalyst, said alum-inate being selected from the group consisting of the alkali metal and alkaline earth metal aluminates and zinc aluminate.

No references cited. 

3. A PROCESS FOR THE MANUFACTURE OF HIGHLY POLYMERIC POLYMETHYLENE TEREPHTHALATES WHICH COMPRISES POLYMERIZING A BIS (HYDROXY ALKYL) TEREPHTHALATE IN THE PRESENCE OF AN ALUMINATE WHICH IS SOLUBLE IN THE REACTION MIXTURE AS A CATALYST, SAID ALUMINATE BEING SELECTED FROM THE GROUP CONSISTING OF THE ALKALI METAL AND ALKALINE EARTH METAL ALUMINATES AND ZINC ALUMINATE. 